1. Field of the Invention
The present invention relates to an electronic circuit for indication of the operational status of a vehicle brake system. More specifically, the present invention relates to an electronic circuit for indication of the operational status of a vehicle brake system where an indicator lamp first is transiently activated to indicate circuit functionality and is then deactivated and remains deactivated once a brake fault has occurred.
2. Description of the Prior Art
Prior art brake wear and adjustment systems connect each sensor to a condition electronics module to generate a signal to the driver or mechanic that brake service is required. Many systems have been developed in the past to provide a signal to a vehicle operator to warn that brake lining wear or actuator travel has progressed a predetermined amount. However, these systems have been generally unsatisfactory due to their complexity and/or unreliability.
Examples of these prior art systems can be found in U.S. Pat. Nos. 3,594,721; 3,716,831; 3,735,343; 3,755,774; 3,869,695 and 3,902,157 the disclosures of which are hereby incorporated by reference, which disclose electronic signaling systems for the detection and notification of abnormal brake wear. One disadvantage with many of these systems is the parallel wiring configuration which results in a large number of conductors that must be used to connect the sensors with the electronic monitoring unit. Another disadvantage is that some prior art systems do not indicate when brake, service is required if a short to ground fault occurs in the detection circuit.
U.S. Pat. No. 3,456,236 discloses a brake shoe wear indicator system where the wear sensors are connected in series to a relay which, when deenergized, closes contacts to light a bulb in a trouble alarm circuit. This concept lacks the reliability required of a brake condition alarm system because it indicates a working brake system when the light is burned out or there exists an open circuit to the bulb. Another problem with many of the prior art brake wear systems is that an electrical current is carried through the wheel bearings which can cause premature failure of the bearing(s). A system that eliminates or reduces electrical current that must be carried through a bearing would be desirable.